Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$181.50	8.362%	$196.677	$196.68	$196.70	$196.70
Purchase #2	$193.56	11.244%	$215.3239	$215.32	$215.30	$215.30
Purchase #3	$78.29	13.527%	$88.8803	$88.88	$88.90	$88.90
Purchase #4	$37.29	7.130%	$39.9488	$39.95	$39.95	$39.90
Purchase #5	$90.69	7.479%	$97.4727	$97.47	$97.45	$97.50
Purchase #6	$45.39	13.734%	$51.6239	$51.62	$51.60	$51.60
Purchase #7	$27.94	12.848%	$31.5297	$31.53	$31.55	$31.50
7 purchase totals =	$654.66		$721.4563	$721.45	$721.45	$721.40